It's a hypothetical about how ubiquitous sloppy use of biometric technologies will fatally undermine the credibility of even the most useful biometric techniques in the criminal justice system.

"Is it possible that the vital cornerstone of our criminal justice system - the forensics of DNA, of biometrics, from fingerprints, to voiceprints - could become too contaminated by the ubiquity of their acquisition and storage in computer systems to be regarded as any kind of evidence at all...

More and more organisations, more and more regimes, are demanding and storing our biometrics in more and more computer systems. We know no computer system is 100% infallible.

In a world where our biometrics are acquired and stored by all types of regimes and organisations, we must be rigorously analytical of the risks involved and where they may lead us. If we do not do so, I believe we run the risk of losing our best evidence, our best defence against organised and serious crime: the very opposite of what was intended. These are not outcomes we should countenance lightly...

We need to think very carefully indeed about where this simplistic belief that biometrics will be a universal panacea to issues of identity could lead. We know that the law of unintended consequences will always undermine our best intentions. And, if that were to happen, there would be no way this particular genie could ever be put back into the bottle. We only have the one set of biometrics, one set of DNA.

If these important issues are not thought through clearly, if we do not have a proper discussion - including of the international dimension - about the way in which biometrics and our DNA are acquired, stored and used, our ability to investigate and prosecute criminals based on forensic evidence could be lost forever."